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COPPER DAM FUR SUREW PROPELLER SHIPS.- No. 303,000. Patented Aug. 5, 1884.

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CHARLES GOODALL, SAN FRANCISCO, CALIFORNIA.

COFFER-DAM FOR SCREW-PROPELLER SHlPS.

SPECIFICATION forming part of Letters Patent No. 303,000, dated August 5, 1884.

Application filed April 24, 1884. (No mode1.)

.To aZZ whom it may concern a lowing is a specification.

The invention relates to all screw-propeller ships which sail long distances from convenient repairing-stations; but it is more particularly intended for use on steamships sent on whaling voyages into theArctic Ocean, where, from the presence of ice, the ships propeller is in almost constant danger of having its blades broken, and the repairing and replacing must be done on the spot.

The invention consists in the combination of parts forming the cotter-dam and the means employed to adjust and hold these parts firmly in position, by which expeditious and effect ive operations may be performed in the matter of completely enveloping the propeller with a water-tight inclosure in which the work gonnected with repairing or replacing may be one.

In the accompanying drawings, forming part of this specification, Figure l is a view of my cotter-dam fastened in place, looking from in front of the rudder toward the bow of the ship. Fig. 2 is a side view. Fig. 3 is a view looking aft. Fig. 4 is a top view of one-half of the coi'ier-dam; and Fig. 5 is a sectional view upon a larger scale than the other figures, showing how the joint may be made.

In all the figures like letters of reference represent like parts. 1

In the drawings 1 show only just so much of the stern of a ship as is necessary to illustrate my device.

A is the continuation of the ships keel. B is the stern-post; O, the rudder-post; D, the rudder; and E is a stout timber, supplied in the present illustration, to prevent the ice from getting into the propeller-well. .Within the rectangular space inclosed by the timbers A, B, C, and E the propeller finds room to revolve, which in the present instance is a twobladed one, as shown in dotted lines, Fig. 2.

F F are half-shells made of stiff wroughtiron plates, having a shape, when joined togethcr, something like a gigantic thimble with flanged edges and sides pressed together so as to be oval, instead of round. The upper rim or the beam E, (see Fig. 4;) and the sides of the shell (see Figs. 1 and 3) may converge toward a meeting point below, but are suddenly brought together by a simple curve at the bottom. The

padded with any suitable paddingas indiarubber or canvas filled with oakum-as in Fig. 5. In fact, any substance that is capable of making a good impervious j oint will do. When the canvas and oakuni is used, there should be a wooden strip, I, bolted to the angle-iron flanges of the half-shells, so as to provide a substance to nail the canvas to. i The vertical tour the ruddenpost or stern-post may have, the horizontal joint at the bottom being ordinarily flat and even.

On the bottom of the interior of the halfshell F there is a staple or eyebolt, J, to which is fastened a chain or rope, K, and on the interior bottom of the other half, F, is secured a grooved face roller, L, under which the chain or rope passes to lead upward to the ships deck, there to be connected with a block and tackle or a Windlass.

At the upper part of the two halves of the coffer-dam is a stout chain, M, anchored to staples N at each side, and upon which chain is a suitableturn-buckle, O,which,when turned around, will tighten or slacken the .joint. A couple of eyebolts, 1?, may be riveted to the outsides of the half-shells to secure ropes to in hauling the parts on deck or lowering them to their places.

The operation is as follows: The two parts are conveniently stowed on the vessel, and form part of her outfit. When a propeller becomes broken and useless, whether in port or at sea, the blades are first set in a vertical line, (for the coffcrdam is not intended to accommodate them when set horizontally, though in cases where the propeller has three or more blades it might be so made,) then with ropes, chains, or tackle of any suitable kind the first half, F, is lowered over the stern until the staple J is below the beam E, when the flange, G,incloses a space large enough to allow a propeller to be taken in or out on either side of joints will be formed to accommodate any confacing-edges H of these shells are flanged and I GO chain K is secured to this staple and the whole is lowered to its proper'position, the chain bein g passed behind the propeller. Afterward the second half, F, is lowered, the end of the chain being first 'rove through the pulley L. When the two parts are adjusted to about their proper position, the chain M is hooked into the staples l, and the turn -buckle screwed around to draw the parts as tightly against the ships timbers as possible. At the same time the chain K is hauled tight, and the joint is thus made water-tight; The water in the coffer .dam is then pumped out and operations 011 the propeller immediately proceeded with.

Vhat I claim as my invention, and desire to secure by Letters Patent, is as follows:

In a coffer-dam for application to screw-propeller vessels to inclose the propeller in a water-tight compartment, the combination of the 

